Weak at the Knees: Wearable Haptic Feedback Device for Real-Time Gait Retraining for Slowing Knee Osteoarthritis

Abstract

Real-time gait retraining has been shown to be a promising non-invasive intervention for patients with early stage medial compartmental knee osteoarthritis. In order for real-time gait retraining to be effective beyond a clinical and laboratory setting, the technology needs to be effective but also portable. This thesis presents a wearable haptic feedback ankle bracelet, which seeks to increase portability of real-time gait retraining systems. A gait retraining scheme is presented, involving the foot progression angle and step width, two gait parameters that are easily modifiable but also influential in reducing peak knee adduction moments (KAM), a surrogate measure for medial tibiofemoral joint loads. Haptic feedback constitutes the first of the two main sections of this work, and is made up of two experiments. Two different haptic modalities were combined into a single device as a means of increasing portability of existing feedback systems while maintaining high user perceptual accuracy. The first experiment investigated lateral skin stretch as a modality for presenting directional feedback cues to participants on the lower limb. Findings show that human perception of directional skin stretch cues are extremely high, given the right speed, displacement and location of the stimulus. The second experiment explored the use of a haptic illusion, tactile apparent movement, as a modality for directional feedback cues on the lower limb. High direction perception accuracy was achieved when the participant received the optimal stimulus duration and interstimulus onset intervals during both standing and walking. The difficulties of integrating lateral skin stretch into a portable and wearable device compared with using tactile apparent movement is discussed. The proposed ankle bracelet combines tactile apparent movement with the widely used modality of binary (on/off) vibrotactile feedback into a single device; thus being capable of eliciting two different directional haptic cues to the user. The second section of the thesis addresses the effectiveness of the ankle bracelet in the area of gait retraining and also consists of two experiments. The first experiment implemented the ankle bracelet as part of a real-time gait retraining task for the gait parameters foot progression angle and step width. Results showed that participants were able to retrain both gait parameters in a single short training session using the ankle bracelet. The type of feedback given (vibrotactile or tactile apparent movement) for either foot progression or step width (vice versa) in general, did not matter. The second experiment investigated the use of a data-driven approach in order to determine participant-specific foot progression angle and step width modifications to reduce the first and second KAM peaks. Results showed that these models were not accurate enough to predict first and second KAM peaks. Despite this undesirable result, it was found that some participant-specific gait modifications altered peak KAMs, by reducing the second peak but increasing the first. This thesis showed that select lower limb gait parameters can be easily trained using the proposed haptic ankle bracelet, improving portability over currently feedback devices. Even though more research is required in developing more accurate participant-specific predictive models of KAM peaks; a scheme involving foot progression angle and step width remains promising as they were able to significantly alter peak KAMs. Real-time haptic gait retraining is an intervention, that has the potential to guide participants to change their walking patterns, which could effectively slow the progression of knee osteoarthritis.